Exhaust System

ABSTRACT

An exhaust system for a plurality of turbines. An exhaust gas outlet is positioned on each of the plurality of turbines. The exhaust gas outlet provides a way of discharging any exhaust gas produced by a turbine during operation of the turbine. A common exhaust is operatively connected to the exhaust gas outlet of each of the plurality of turbines. The common exhaust is disposed to receive any exhaust gas produced by the plurality of turbines during the operation of at least one of the turbines. A back flow damper is positioned on the exhaust gas outlet for each of the plurality of turbines. An isolation damper is disposed on the back flow damper. The isolation damper is in fluid communication with the common exhaust.

CROSS REFERENCES

This application claims the benefit of provisional patent applicationNo. 61/461,124 filed on Jan. 13, 2011.

BACKGROUND OF THE INVENTION

The present invention is an exhaust system that is used in powergenerating systems.

In power generating systems there are frequently several powergenerating devices that are coupled together to proved power for afacility. The power generating devices produce exhaust gases and it isdesirable to use the exhaust gases to power other devices. Accordingly,there is a need in the industry for a common exhaust system that cancombine the exhaust gases from several power generating devices and usethe exhaust gases to operate or power other devices. The inventionprovides such an exhaust system that combines the exhaust gases tooperate other devices to enhance the efficiency of the power generatingsystem.

SUMMARY OF THE INVENTION

The present invention is directed to an exhaust system for a pluralityof turbines. An exhaust gas outlet is positioned on each of theplurality of turbines. The exhaust gas outlet provides a way ofdischarging any exhaust gas produced by a turbine during operation ofthe turbine. A common exhaust is operatively connected to the exhaustgas outlet of each of the plurality of turbines. The common exhaust isdisposed to receive any exhaust gas produced by the plurality ofturbines during the operation of at least one of the turbines. A backflow damper is positioned on the exhaust gas outlet for each of theplurality of turbines. The back flow damper allows exhaust gas to exitthe turbine and prevents fluids in the common exhaust from entering theturbine. An isolation damper is disposed on the back flow damper. Theisolation damper is in fluid communication with the common exhaust. Theisolation damper is operable to control fluid flow between the back flowdamper and the common exhaust. A drain is positioned adjacent theisolation damper to drain any fluid that maybe present during the timethat the isolation damper does not allow fluid flow from the back flowdamper to the common exhaust.

The exhaust system allows the turbines to be utilized only as needed andavoids potential damage to turbines that are taken out of service.

Other objects and advantages of the present invention will becomeapparent to those skilled in the art upon a review of the followingdetailed description of the preferred embodiments and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plane view of the arrangement of several turbines connectedto a common exhaust.

FIG. 2 is a side elevation view of the features of the exhaust outlet ona single turbine.

FIG. 3 is a side elevation view of an alternative arrangement on asingle turbine for the exhaust outlet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The following describes a method and apparatus to operate a set of heatengines or turbines connected to a common exhaust line in such a way asto securely prevent damage to non-operating units by operating units.

Heat engines that produce electricity, such as turbines, also produce ahot exhaust stream. The hot exhaust stream represents useful energy. Itis useful to combine the exhaust of more than one turbine into acombined stream to supply thermal energy in the form of hot exhaust gasto other equipment such as heat exchangers or absorption chillers. Thisapparatus and method accomplishes that combined exhaust while securelypreventing damage to other heat engines connected to the common exhaustduct.

It is difficult to operate heat engines that connect to a common exhaustduct because the exhaust pressurizes the common duct and exhaust from anoperating engine can be forced into a non-operating unit resulting indamage. The features of the invention will be described using turbine asthe heat engines. It should be understood, however, that other heatengines can be utilized with the invention. FIG. 1 shows severalturbines 7, each having an exhaust outlet 9 connected to a commonexhaust duct 15. The combined exhaust in this case is used to operate aheat exchanger 19 and an absorption chiller 21.

FIG. 2 show details of the apparatus and method to prevent exhaust froman operating engine from entering a non-operating engine. The exhaustoutlet 9 incorporates a back-flow damper 25 that is positioned adjacentthe turbine. The back-flow damper is a passive device for preventingflow from a pressurized duct into a non-operating turbine. It consistsof a flapper 27 on a hinge 29 and a seating surface 31. The flapperswings on the hinge such that it permits exhaust to exit the engine whenit runs, but swings the opposite way preventing flow from a pressurizedduct, such as the common exhaust 15, from entering the engine when it isnot operating. The back-flow damper 25 has the advantage that it willoperate with no outside manipulation when the engine starts and when itshuts down. The back-flow damper has the disadvantage that it mustoperate freely and closes with only the pressure of the exhaust gases inthe common duct to force it closed. In practice, back-flow dampers 25allow some leakage past the flapper when the damper is in the closedposition.

An active isolation damper valve 35 with a powered operator 37 isarranged in series in the exhaust outlet 9 with the back-flow damper 25.The isolation damper valve 35 is positioned on the side of the back-flowdamper that is spaced apart from the turbine 7. The active damper valve35 is operatively connected to the common exhaust duct 15. The activedamper valve forms a boundary to prevent flow from the pressurizedcommon exhaust duct into a non-operating engine when the isolationdamper valve is closed. This active damper valve has the advantage thatit forms a secure boundary to prevent flow from the common exhaust duct.The active damper valve 35 has the disadvantage that it is slow tooperate and the operator of the valve must have knowledge of theoperating state of the heat engine. The active damper valve 35 cannot beclosed if the turbine 7 is being operated as damage to the turbine couldresult. It also has the disadvantage that although it can seatrelatively securely, it may allow slow leakage of exhaust into theexhaust outlet 9 the non-operating heat engine or turbine from apressurized duct, such as the common exhaust 15.

A vent line 41 is positioned between the back flow damper 25 and theisolation damper 35. The vent line is arranged to allow any exhaust thatmay leak past the active isolation damper 35 to escape and preventbuild-up of pressure in the space between the active damper valve andthe passive back-flow damper. A valve 43 is positioned on the vent line41 to allow the vent line to be open or closed. The vent line is open tothe atmosphere unless the valve 43 is closed.

A drain line 45 is positioned on the side of the active damper 35 thatis spaced apart from the vent line 41. The vent line is disposed toprevent condensation or rain water that may enter the duct from contactwith the active damper valve 35. A valve 47 is positioned on the drainline to allow the drain line to be open or closed. The drain line isopen to a floor drain or other suitable drain unless the valve 47 isclosed.

In the event that a turbine 7 is off-line and other turbines that areconnected to the common exhaust 15 are operating, the potential existsfor problems.

In the absence of other measures, exhaust gas from the on-line turbines7 can leak past the back-flow damper 25 into the off-line turbine. Ifthis happens, water vapor can condense in the turbine causing damageover time. Most manufactures discourage operation in this mode as amatter of practice or require that the off-line turbines be isolatedfrom the common duct 15 by means of inserting a blank flange if aturbine is off-line for more than a day.

The exhaust outlet leading from the off-line turbine will also cool.Moist exhaust gas from the on-line turbines will migrate into the coolexhaust outlet and condense. Over time, water may accumulate in theexhaust outlet.

The block and vent arrangement shown in FIGS. 1 and 2 avoids theseproblematic conditions. This arrangement consists of a back-flow damper25 that is installed at the turbine exhaust outlet 9. A butterfly orisolation damper 35 is installed on the back-flow damper outlet. When aturbine 7 is off-line, leakage of exhaust from the common exhaust ductpast the isolation damper valve 31 is vented outside through the ventline 41. Accordingly, there is little or no driving pressure to forceexhaust gas past the back-flow damper and into the turbine. A drain 45for the exhaust outlet is located as close as possible to the downstreamside of the isolation damper 31. The drain allows any accumulated waterto drain. The passive back flow damper 25 will open from the force ofthe exhaust gases produced by the operating turbine 7. The inventionincludes a positive interlock to assure the isolation damper 35 isopened prior to turbine start. FIG. 3 shows another embodiment of theinvention where a blower 51 or other source of air under pressure isconnected to the vent line 41 on the side of the valve 43 that is spacedapart from the isolation damper 35.

When a turbine 7 is off-line or not operating, clean ambient air issupplied to the space between the back flow damper 25 and the isolationdamper 35 by the blower 51. The air from the blower pressurizes thespace between the dampers in excess of the pressure in the turbinecommon exhaust duct 15 (to 12 inches of water for example). The airunder pressure causes the flapper 27 of the back flow damper 25 to beheld against the seating surface 31 and to close the back flow damper.This essentially closes the off-line turbine 7 from the common exhaust15. At the same time the pressure of the air from the blower keepsexhaust gases from the common exhaust from leaking past the closedisolation damper 35 as the air from the blower is at a higher pressurethan the exhaust gases in the common exhaust. Leakage of clean air mayoccur into the turbine or the exhaust duct, but at a small rate.

The operation of the system shown in FIG. 3 is essentially the same asthe operation of the invention described with respect to FIGS. 1 and 2.The blower 51, however, should be turned off before the turbine isstarted.

The above detailed description of the present invention is given forexplanatory purposes. It will be apparent to those skilled in the artthat numerous changes and modifications can be made without departingfrom the scope of the invention. Accordingly, the whole of the foregoingdescription is to be construed in an illustrative and not a limitativesense, the scope of the invention being defined solely by the appendedclaims.

1. An exhaust system for a plurality of turbines comprising: an exhaustgas outlet positioned on each of the plurality of turbines, the exhaustgas outlet providing a way of discharging any exhaust gas produced by aturbine during operation of the turbine; a common exhaust operativelyconnected to the exhaust gas outlet of each of the plurality ofturbines, the common exhaust disposed to receive any exhaust gasproduced by the plurality of turbines during the operation of at leastone of the turbines; a back flow damper position on the exhaust gasoutlet for each of the plurality of turbines, the back flow damperallowing exhaust gas to exit the turbine and preventing fluids in thecommon exhaust from entering the turbine; an isolation damper disposedon the back flow damper, the isolation damper being in fluidcommunication with the common exhaust, the isolation damper beingoperable to control fluid flow between the back flow damper and thecommon exhaust; and a drain positioned adjacent the isolation damper todrain any fluid that maybe present.
 2. An exhaust system of claim 1wherein a conduit is connected to the isolation damper and a valve ispositioned in the conduit to control the flow of fluid through theconduit.
 3. The exhaust system of claim 2 wherein the conduit is open tothe atmosphere and the valve can be opened to exhaust any fluids fromthe common exhaust that are present in the isolation damper.
 4. Theexhaust system of claim 2 wherein a source of pressurized fluid isconnected to the conduit whereby the valve can be opened to admitpressurized fluid to isolation damper to pressurize the isolation damperand back flow damper to a pressure greater than the pressure in thecommon exhaust.